Blair Montgomery Thornton (born July 23, 1950) is a Canadian guitarist and songwriter most widely known for his work with the Canadian rock band Bachman-Turner Overdrive (BTO). He also played in the Vancouver-based band prior to joining BTO. Thornton joined the group in early 1974 during the supporting tour for the Bachman-Turner Overdrive II album, replacing Tim Bachman shortly after that album was released. Thornton made his live debut with BTO at a March 1974 televised event for Don Kirshner's In Concert program hosted by .